Some embodiments relate to semiconductor power devices. A power device is capable of switching relatively high currents and/or at relatively high voltages. Such currents may be in the order of one to hundreds of Amperes and such voltages may be in the order of a few hundreds to thousands of Volts. Some embodiments further relate to assembling a semiconductor power device.
U.S. Pat. No. 7,859,079B2, which is incorporated by reference, discloses a switching power semiconductor device that includes at least two substrates. The substrates are arranged substantially parallel to each other. The surfaces of the substrates and the surfaces of semiconductor elements arranged on the substrates may include electrodes. A subset of the electrodes face each other and electrical connections are provided between them. In an embodiment, the electrical connections are provided by copper balls that are interposed between two electrodes and that are soldered to the electrodes. In another embodiment, drop-shaped elements of solder or lead are provided between two electrodes. In yet another embodiment, drop-shaped elements of solder or lead are provided on electrodes of one of the substrates, and copper balls are interposed between the drop-shaped elements and electrode of the other one of the substrates. The copper balls and/or the drop-shaped elements have a size that is adapted to a required distance between the electrodes between which they are interposed such that the two substrates are arranged substantially parallel to each other. The copper-balls and/or the drop-shaped elements provide an electrical connection between different electrical elements of the two substrates. In addition, heat can be transported away from the semiconductor elements provided on the substrates via the copper-balls and/or the drop-shaped elements.
The copper balls and/or the drop-shaped elements of the above discussed patent application provide a spacing between the two substrates and, thereby, define a distance between the two substrates. In the following of this document, it is assumed that a line that forms the shortest distance between the two substrates is a z-dimension. Thus, in other words, the copper balls and/or the drop-shaped elements define, in the z-dimension, a relative position of the two substrates with respect to each other. In the following of this document it is further assumed that the x-dimension and the y-dimension are oriented perpendicular to the above discussed z-dimension. Hence, a 3-dimensional Cartesian coordinate system is assumed. When, in the above cited patent publication, the first substrate and the second substrate are exactly flat and the copper balls have a size such that the two substrates are arranged exactly parallel to each other, the x-dimension and the y-dimension define a virtual plane that is also parallel to the two substrates.